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Kidney Week

Abstract: TH-PO854

Serum Bicarbonate but Not Urine Ammonium Predicts Renal Outcomes in Polycystic Kidney Disease

Session Information

Category: Genetic Diseases of the Kidneys

  • 1001 Genetic Diseases of the Kidneys: Cystic

Authors

  • Blijdorp, Charles J., Erasmus Medical Center, Rotterdam, Netherlands
  • Severs, David, Erasmus Medical Center, Rotterdam, Netherlands
  • Gansevoort, Ron T., University Medical Center Groningen, Groningen, Netherlands
  • Zietse, Robert, Erasmus Medical Center, Rotterdam, Netherlands
  • Hoorn, Ewout J., Erasmus Medical Center, Rotterdam, Netherlands

Group or Team Name

  • DIPAK consortium
Background

Recently, urine ammonium (uNH4+) was shown to better predict renal outcomes in CKD than serum bicarbonate (sBic). Urinary acidification is impaired in patients with autosomal dominant polycystic kidney disease (ADPKD). Our aim was to analyze whether sBic or uNH4+ predicts renal outcomes in ADPKD.

Methods

We studied the predictive value of baseline sBic and uNH4+for worsening kidney function (30% decrease in eGFR or ESRD) in 305 ADPKD patients from the DIPAK-1 trial (lanreotide vs. placebo). Secondary outcomes were eGFR slope and change in height-adjusted total kidney volume (hTKV). Patients were followed for 2.5 years with monitoring of eGFR and 24-hour urine every 3 months. uNH4+ was measured using a phenol-hypochlorite reaction in 24-hour urine. Logistic regression was used for analysis. The fully adjusted model included age, sex, eGFR, albuminuria, serum potassium, hTKV, PKD mutation, treatment group, hospital, BMI, cardiovascular disease, hypertension, net endogenous acid production (NEAP) and sBic or uNH4+.

Results

A lower sBic at baseline was associated with worse renal outcomes (adjusted hazard ratio lowest vs. highest sBic tertile 2.68, 95% CI 1.11 to 6.46, Figure). A lower sBic at baseline was also associated with steeper eGFR slope (p=0.01), and greater increase in hTKV (p=0.05). As expected, uNH4+correlated with dietary protein intake and NEAP (r 0.45 and 0.26, P<0.0001). However, uNH4+was not associated with the primary and secondary outcomes in both the unadjusted and adjusted models (Figure).

Conclusion

sBic but not uNH4+predicts renal outcomes in ADPKD. These findings support the notion that mechanisms of disease progression in ADPKD differ from other causes of CKD.

Funding

  • Private Foundation Support